It is known in the art to use excimer lasers having pulse durations in the nanosecond range and wavelengths in the ultraviolet range for microstructurings. A laser microstructuring of wear-resistant surfaces of solid bodies is mainly required for embossing rollers or embossing dies when these embossing rollers or dies are e.g. intended for embossing fraud-resistant authentication features or particular optical diffraction attractive signs on packaging foils for cigarettes or foods. Such packaging foils are mostly made up of a paper or plastics layer provided with a vapor-deposited or sputtered metal layer, or they are entirely made of metal, mostly aluminum, or entirely of paper or plastics with a surface treatment that produces the optically and optical diffraction effective features and structures. In this respect, masks or diaphragms are preferably used to shape the intensity profile of the laser beam.
WO 2007/012215 to the applicant of the present invention discloses the creation of so-called ripples by means of a femtosecond laser on a workpiece that may be provided with a hard material layer consisting of superhard amorphous carbon having a fraction of more than 50% of diamond-like sp3 bonds known under the designation ta-C, of tungsten carbide, WC, boron carbide, B4C, silicon carbide, SiC, or similar hard materials. As appears from different documents available in the Internet, mainly the superhard amorphous carbon films, ta-C, are very suitable for various applications, more particularly for tribological applications but also for optical diffraction applications.